A facile method for studying competitive sorption from binary mixtures of dyes

Textile industry produces a great variety of effluents, rich in dyes, which have to be treated, in order to eliminate (or to decrease to secure levels) the contents of these environmentally harmful substances. The first step is the quantitative determination of dye concentrations in the effluent. In this manuscript, we propose a simple method to determine dye concentrations in solutions with two different dyes: acid blue 260, AB, and methyl orange, MO. It was demonstrated that correlating the apparent molar absorptivity of one of the dyes with the concentration of the other dye, a numerical method can be used to determine both dye concentrations and relative errors, using a single value of absorbance for each dye. The method was applied to the sorption of AB and MO on crosslinked chitosan, C-CHIT, and the more effective sorption of AB could be characterized by the determination of different isotherm parameters, estimation of Gibbs free energy of adsorption, as well as competitive sorption by itself.